Designation Design ation:: C31/C31 C31/C31M M – 10
Standard Practice for
Making and Curing Concrete Test Specimens in the Field 1 This standard is issued under the fixed designation C31/C31M; the number immediately following the designation indicates the year of original origin al adoption or, in the case of revis revision, ion, the year of last revision. revision. A number in paren parenthese thesess indicates the year of last reappr reapproval. oval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense.
1. Sco Scope* pe* 1.1 This practice covers covers procedures procedures for making and curing cylinder and beam specimens from representative samples of fresh concrete for a construction project. 1.2 The concrete concrete used to make the molded specimens specimens shall be sampled after all on-site adjustments have been made to the mixture proportions, including the addition of mix water and admixtures. This practice is not satisfactory for making specimens from concrete not having measurable slump or requiring other sizes or shapes of specimens. 1.3 The values stated in either SI units or inch-pound inch-pound units are to be regarded separately as standard. The values stated in each system may not be exa exact ct equ equiva ivalen lents; ts; the theref refore ore,, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. standard d doe doess not purport purport to add addre ress ss all of the 1.4 This standar safet sa fetyy co conc ncer erns ns,, if an anyy, as asso socia ciate ted d wi with th its us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applica (Warning —Fresh bility of regulatory limitations prior to use. ( Warning—Fresh hydrau hyd raulic lic ceme cementi ntitiou tiouss mix mixtur tures es are cau causti sticc and may cau cause se chemica che micall bur burns ns to exp expose osed d ski skin n and tiss tissue ue upo upon n pro prolon longed ged 2 exposure. ) 1.5 The text of this standa standard rd references references notes which provide provide explanatory material. These notes shall not be considered as requirements of the standard. 2. Referenc Referenced ed Documents Documents 2.1 ASTM Standards:3 C125 Terminology Relating to Concrete and Concrete Aggregates
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This practice is under the jurisd jurisdiction iction of ASTM Commi Committee ttee C09 C09 on Concrete and Concrete Aggregate Aggregatess and is the direct responsibility responsibility of Subco Subcommitte mmitteee C09.61 on Testing for Strength. Current edition approved Oct. 1, 2010. Published November 2010. Originally approved in 1920. Last previous edition approved in 2009 as C31/C31M–09. DOI: 10.1520/C0031_C0031M-10. 2 See Section on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol. 04.02. 3 For refere referenced nced ASTM stand standards, ards, visit the ASTM websi website, te, www www.astm .astm.org .org,, or contact ASTM Customer Service at
[email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
C138/C138M Test Test Me Metho thod d fo forr Den Densit sity y (U (Unit nit Weig eight) ht),, Yield, and Air Content (Gravimetric) of Concrete C143/C143M Test Method for Slump of Hydraulic-Cement Concrete C172 Practice for Sampling Freshly Mixed Concrete C173/C173M Test Test Me Meth thod od fo forr Ai Airr Co Cont nten entt of Fr Fres eshl hly y Mixed Concrete by the Volumetric Method C231 Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method C330 Specification Specification for Lightw Lightweight eight Aggregates Aggregates for Structural Concre Concrete te C403/C403M Test Method for Time of Settin Setting g of Concr Concrete ete Mixtures by Penetration Resistance C470/C470M Specific Specificatio ation n for Mol Molds ds for For Formin ming g Con Con-crete Test Cylinders Vertically C511 Spec Specific ificatio ation n for Mix Mixing ing Roo Rooms, ms, Moi Moist st Cab Cabine inets, ts, Mois Mo istt Ro Room oms, s, an and d Wate aterr St Stor orag agee Tan anks ks Us Used ed in th thee Testing of Hydraulic Cements and Concretes C617 Practice for Capping Cylindrical Concrete Specimens C1064/C1064M Test Test Method for Tempera emperature ture of Fresh Freshly ly Mixed Hydraulic-Cement Concrete Concrete Institute Publication:4 2.2 American Concrete CP-1 Concrete Field Testing Technician, Grade I 309R Guide for Consolidation of Concrete ` , , ` , ` , , ` , , ` ` ` ` ` , , , , , ` , ` ` , ` ` ` ` , ` ` ` ` , , , ` -
3. Terminology 3.1 For definitio definitions ns of ter terms ms use used d in thi thiss pra practic ctice, e, ref refer er to Terminology C125 C125.. 4. Signi Significanc ficancee and Use 4.1 Thi Thiss pra practic cticee pro provid vides es stan standar dardiz dized ed req requir uiremen ements ts for making mak ing,, cur curing ing,, pro protect tecting ing,, and tra transp nsport orting ing con concre crete te tes testt specimens specim ens under field condi conditions. tions. 4.2 4. 2 If th thee sp speci ecime mens ns ar aree ma made de an and d st stan anda dard rd cu cure red, d, as stipulat stip ulated ed her herein, ein, the res result ulting ing str streng ength th test dat dataa whe when n the specim spe cimens ens are tes tested ted are abl ablee to be used for the fol follow lowing ing purposes: 4.2.1 Accept Acceptance ance testing for specifi specified ed strength, 4.2.2 4.2 .2 Checkin Checking g ade adequa quacy cy of mix mixtur turee pr propo oporti rtion onss for strength, and
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Available from American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094, http://www.aci-int.org.
*A Summary of Changes section appears at the end of this standard. Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Copyright ASTM International Provided by IHS under license with ASTM No reproduction or networking permitted without license from IHS
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C31/C31M – 10 4.2.3 Quality control. 4.3 If the specimens are made and field cured, as stipulated herein, the resulting strength test data when the specimens are tested are able to be used for the following purposes: 4.3.1 Determination of whether a structure is capable of being put in service, 4.3.2 Comparison with test results of standard cured specimens or with test results from various in-place test methods, 4.3.3 Adequacy of curing and protection of concrete in the structure, or 4.3.4 Form or shoring removal time requirements. 5. Apparatus 5.1 Molds, General— Molds for specimens or fastenings thereto in contact with the concrete shall be made of steel, cast iron, or other nonabsorbent material, nonreactive with concrete containing portland or other hydraulic cements. Molds shall hold their dimensions and shape under all conditions of use. Molds shall be watertight during use as judged by their ability to hold water poured into them. Provisions for tests of water leakage are given in the Test Methods for Elongation, Absorption, and Water Leakage section of Specification C470/C470M. A suitable sealant, such as heavy grease, modeling clay, or microcrystalline wax shall be used where necessary to prevent leakage through the joints. Positive means shall be provided to hold base plates firmly to the molds. Reusable molds shall be lightly coated with mineral oil or a suitable nonreactive form release material before use. 5.2 Cylinder Molds— Molds for casting concrete test specimens shall conform to the requirements of Specification C470/C470M. 5.3 Beam Molds—Beam molds shall be of the shape and dimensions required to produce the specimens stipulated in 6.2. The inside surfaces of the molds shall be smooth. The sides, bottom, and ends shall be at right angles to each other and shall be straight and true and free of warpage. Maximum variation from the nominal cross section shall not exceed 1 ⁄ 8 in. [3 mm] for molds with depth or breadth of 6 in. [150 mm] or more. Molds shall produce specimens at least as long but not more than 1 ⁄ 16 in. [2 mm] shorter than the required length in 6.2. 5.4 Tamping Rod —A round, smooth, straight, steel rod with a diameter conforming to the requirements in Table 1. The length of the tamping rod shall be at least 4 in. [100 mm] greater than the depth of the mold in which rodding is being performed, but not greater than 24 in. [600 mm] in overall length (see Note 1). The rod shall have the tamping end or both ends rounded to a hemispherical tip of the same diameter as the rod. ` , , , ` ` ` ` , ` ` ` ` , ` ` , ` , , , , , ` ` ` ` ` , , ` , , ` , ` , , ` -
NOTE 1—A rod length of 16 in. [400 mm] to 24 in. [600 mm] meets the requirements of the following: Practice C31/C31M, Test Method C138/ C138M, Test Method C143/C143M, Test Method C173/C173M, and Test Method C231.
5.5 Vibrators—Internal vibrators shall be used. The vibrator frequency shall be at least 9000 vibrations per minute [150 Hz] while the vibrator is operating in the concrete. The diameter of a round vibrator shall be no more than one-fourth the diameter of the cylinder mold or one-fourth the width of the beam mold. Other shaped vibrators shall have a perimeter equivalent to the Copyright ASTM International Provided by IHS under license with ASTM No reproduction or networking permitted without license from IHS
TABLE 1 Tamping Rod Diameter Requirements Diameter of Cylinder or Width of Beam in. [mm] 8 [200]
TABLE 4 Molding Requirements by Vibration
7. Sampling Concrete
$
TABLE 3 Molding Requirements by Rodding
Specimen Type and Size
Number of Layers
Number of Vibrator Insertions per Layer
Approximate Depth of Layer, in. [mm]
Cylinders: Diameter, in. [mm] 4 [100] 6 [150] 9 [225]
2 2 2
1 2 4
one-half depth of specimen one-half depth of specimen one-half depth of specimen
Beams: Width, in. [mm] 6 [150] to 8 [200] over 8 [200]
1 2 or more
see 9.4.2 see 9.4.2
depth of specimen 8 [200] as near as practicable
perimeter of the mold opening to ensure an even distribution of the concrete with minimal segregation. Each layer of concrete shall be consolidated as required. In placing the final layer, add an amount of concrete that will fill the mold after consolidation. 9.3 Casting Beams— Select the proper tamping rod from 5.4 and Table 1 or proper vibrator from 5.5. Determine the method of consolidation from Table 2, unless another method is specified. If the method of consolidation is rodding, determine the molding requirements from Table 3. If the method of consolidation is vibration, determine the molding requirements from Table 4. Determine the number of roddings per layer, one for each 2 in. 2 [14 cm2] of the top surface area of the beam. Select a placement tool as described in 5.7. Using the scoop or shovel, place the concrete in the mold to the height required for each layer. Place the concrete so that it is uniformly distributed within each layer with minimal segregation. Each layer shall be consolidated as required. In placing the final layer, add an amount of concrete that will fill the mold after consolidation. 9.4 Consolidation— The methods of consolidation for this practice are rodding or internal vibration. 9.4.1 Rodding—Place the concrete in the mold in the required number of layers of approximately equal volume. Rod each layer uniformly over the cross section with the rounded end of the rod using the required number of strokes. Rod the bottom layer throughout its depth. In rodding this layer, use care not to damage the bottom of the mold. For each upper layer, allow the rod to penetrate through the layer being rodded and into the layer below approximately 1 in. [25 mm]. After 3Licensee=Dept of Transportation/5950087001 Not for Resale, 11/17/2010 16:54:45 MST
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C31/C31M – 10 each layer is rodded, tap the outsides of the mold lightly 10 to 15 times with the mallet to close any holes left by rodding and to release any large air bubbles that may have been trapped. Use an open hand to tap light-gauge single-use cylinder molds which are susceptible to damage if tapped with a mallet. After tapping, spade each layer of the concrete along the sides and ends of beam molds with a trowel or other suitable tool. Underfilled molds shall be adjusted with representative concrete during consolidation of the top layer. Overfilled molds shall have excess concrete removed. 9.4.2 Vibration—Maintain a uniform duration of vibration for the particular kind of concrete, vibrator, and specimen mold involved. The duration of vibration required will depend upon the workability of the concrete and the effectiveness of the vibrator. Usually sufficient vibration has been applied as soon as the surface of the concrete has become relatively smooth and large air bubbles cease to break through the top surface. Continue vibration only long enough to achieve proper consolidation of the concrete (see Note 5). Fill the molds and vibrate in the required number of approximately equal layers. Place all the concrete for each layer in the mold before starting vibration of that layer. In compacting the specimen, insert the vibrator slowly and do not allow it to rest on the bottom or sides of the mold. Slowly withdraw the vibrator so that no large air pockets are left in the specimen. When placing the final layer, avoid overfilling by more than 1 ⁄ 4 in. [6 mm]. NOTE 5—Generally, no more than 5 s of vibration should be required for each insertion to adequately consolidate concrete with a slump greater than 3 in. [75 mm]. Longer times may be required for lower slump concrete, but the vibration time should rarely have to exceed 10 s per insertion.
9.4.2.1 Cylinders—The number of insertions of the vibrator per layer is given in Table 4. When more than one insertion per layer is required distribute the insertion uniformly within each layer. Allow the vibrator to penetrate through the layer being vibrated, and into the layer below, about 1 in. [25 mm]. After each layer is vibrated, tap the outsides of the mold at least 10 times with the mallet, to close holes that remain and to release entrapped air voids. Use an open hand to tap cardboard and single-use metal molds that are susceptible to damage if tapped with a mallet. 9.4.2.2 Beams—Insert the vibrator at intervals not exceeding 6 in. [150 mm] along the center line of the long dimension of the specimen. For specimens wider than 6 in., use alternating insertions along two lines. Allow the shaft of the vibrator to penetrate into the bottom layer about 1 in. [25 mm]. After each layer is vibrated, tap the outsides of the mold sharply at least 10 times with the mallet to close holes left by vibrating and to release entrapped air voids. 9.5 Finishing—Perform all finishing with the minimum manipulation necessary to produce a flat even surface that is level with the rim or edge of the mold and that has no depressions or projections larger than 1 ⁄ 8 in. [3.3 mm]. 9.5.1 Cylinders—After consolidation, finish the top surfaces by striking them off with the tamping rod where the consistency of the concrete permits or with a handheld float or trowel. If desired, cap the top surface of freshly made cylinders with a thin layer of stiff portland cement paste which is permitted to ` , , , ` ` ` ` , ` ` ` ` , ` ` , ` , , , , , ` ` ` ` ` , , ` , , ` , ` , , ` -
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harden and cure with the specimen. See section on Capping Materials of Practice C617. 9.5.2 Beams—After consolidation of the concrete, use a handheld float or trowel to strike off the top surface to the required tolerance to produce a flat, even surface. 9.6 Identification— Mark the specimens to positively identify them and the concrete they represent. Use a method that will not alter the top surface of the concrete. Do not mark the removable caps. Upon removal of the molds, mark the test specimens to retain their identities. 10. Curing 10.1 Standard Curing— Standard curing is the curing method used when the specimens are made and cured for the purposes stated in 4.2. 10.1.1 Storage—If specimens cannot be molded at the place where they will receive initial curing, immediately after finishing move the specimens to an initial curing place for storage. The supporting surface on which specimens are stored shall be level to within 1 ⁄ 4 in. per ft [20 mm per m]. If cylinders in the single use molds are moved, lift and support the cylinders from the bottom of the molds with a large trowel or similar device. If the top surface is marred during movement to place of initial storage, immediately refinish. 10.1.2 Initial Curing— Immediately after molding and finishing, the specimens shall be stored for a period up to 48 h in a temperature range from 60 and 80 °F [16 and 27 °C] and in an environment preventing moisture loss from the specimens. For concrete mixtures with a specified strength of 6000 psi [40 MPa] or greater, the initial curing temperature shall be between 68 and 78 °F [20 and 26 °C]. Various procedures are capable of being used during the initial curing period to maintain the specified moisture and temperature conditions. An appropriate procedure or combination of procedures shall be used (Note 6). Shield all specimens from the direct sunlight and, if used, radiant heating devices. The storage temperature shall be controlled by use of heating and cooling devices, as necessary. Record the temperature using a maximum-minimum thermometer. If cardboard molds are used, protect the outside surface of the molds from contact with wet burlap or other sources of water. NOTE 6—A satisfactory moisture environment can be created during the initial curing of the specimens by one or more of the following procedures: (1) immediately immerse molded specimens with plastic lids in water saturated with calcium hydroxide, (2) store in properly constructed wooden boxes or structures, (3) place in damp sand pits, (4) cover with removable plastic lids, (5) place inside plastic bags, or (6) cover with plastic sheets or nonabsorbent plates if provisions are made to avoid drying and damp burlap is used inside the enclosure, but the burlap is prevented from contacting the concrete surfaces. A satisfactory temperature environment can be controlled during the initial curing of the specimens by one or more of the following procedures: (1) use of ventilation, (2) use of ice, (3) use of thermostatically controlled heating or cooling devices, or (4) use of heating methods such as stoves or light bulbs. Other suitable methods may be used provided the requirements limiting specimen storage temperature and moisture loss are met. For concrete mixtures with a specified strength of 6000 psi [40 MPa] or greater, heat generated during the early ages may raise the temperature above the required storage temperature. Immersion in water saturated with calcium hydroxide may be the easiest method to maintain the required storage temperature. When specimens are to be immersed in water
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C31/C31M – 10 saturated with calcium hydroxide, specimens in cardboard molds or other molds that expand when immersed in water should not be used. Early-age strength test results may be lower when stored at 60 °F [16 °C] and higher when stored at 80 °F [27 °C]. On the other hand, at later ages, test results may be lower for higher initial storage temperatures.
10.1.3 Final Curing: 10.1.3.1 Cylinders—Upon completion of initial curing and within 30 min after removing the molds, cure specimens with free water maintained on their surfaces at all times at a temperature of 73.5 6 3.5 °F [23.0 6 2.0 °C] using water storage tanks or moist rooms complying with the requirements of Specification C511, except when capping with sulfur mortar capping compound and immediately prior to testing. When capping with sulfur mortar capping compound, the ends of the cylinder shall be dry enough to preclude the formation of steam or foam pockets under or in cap larger than 1 ⁄ 4 in. [6 mm] as described in Practice C617. For a period not to exceed 3 h immediately prior to test, standard curing temperature is not required provided free moisture is maintained on the cylinders and ambient temperature is between 68 and 86 °F [20 and 30 °C]. 10.1.3.2 Beams—Beams are to be cured the same as cylinders (see 10.1.3.1) except that they shall be stored in water saturated with calcium hydroxide at 73.5 6 3.5 °F [23.0 6 2.0 °C] at least 20 h prior to testing. Drying of the surfaces of the beam shall be prevented between removal from water storage and completion of testing. NOTE 7—Relatively small amounts of surface drying of flexural specimens can induce tensile stresses in the extreme fibers that will markedly reduce the indicated flexural strength.
10.2 Field Curing— Field curing is the curing method used for the specimens made and cured as stated in 4.3. 10.2.1 Cylinders—Store cylinders in or on the structure as near to the point of deposit of the concrete represented as possible. Protect all surfaces of the cylinders from the elements in as near as possible the same way as the formed work. Provide the cylinders with the same temperature and moisture environment as the structural work. Test the specimens in the moisture condition resulting from the specified curing treatment. To meet these conditions, specimens made for the purpose of determining when a structure is capable of being put in service shall be removed from the molds at the time of removal of form work. 10.2.2 Beams—As nearly as practicable, cure beams in the same manner as the concrete in the structure. At the end of 48 6 4 h after molding, take the molded specimens to the storage location and remove from the molds. Store specimens representing pavements of slabs on grade by placing them on the ground as molded, with their top surfaces up. Bank the sides and ends of the specimens with earth or sand that shall be ` , , , ` ` ` ` , ` ` ` ` , ` ` , ` , , , , , ` ` ` ` ` , , ` , , ` , ` , , ` -
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kept damp, leaving the top surfaces exposed to the specified curing treatment. Store specimens representing structure concrete as near the point in the structure they represent as possible, and afford them the same temperature protection and moisture environment as the structure. At the end of the curing period leave the specimens in place exposed to the weather in the same manner as the structure. Remove all beam specimens from field storage and store in water saturated with calcium hydroxide at 73.5 6 3.5 °F [23.0 6 2.0 °C] for 24 6 4 h immediately before time of testing to ensure uniform moisture condition from specimen to specimen. Observe the precautions given in 10.1.3.2 to guard against drying between time of removal from curing to testing. 10.3 Structural Lightweight Concrete Curing—Cure structural lightweight concrete cylinders in accordance with Specification C330. 11. Transportation of Specimens to Laboratory 11.1 Prior to transporting, cure and protect specimens as required in Section 10. Specimens shall not be transported until at least 8 h after final set. (See Note 8). During transporting, protect the specimens with suitable cushioning material to prevent damage from jarring. During cold weather, protect the specimens from freezing with suitable insulation material. Prevent moisture loss during transportation by wrapping the specimens in plastic, wet burlap, by surrounding them with wet sand, or tight fitting plastic caps on plastic molds. Transportation time shall not exceed 4 h. NOTE 8—Setting time may be measured by Test Method C403/C403M.
12. Report 12.1 Report the following information to the laboratory that will test the specimens: 12.1.1 Identification number, 12.1.2 Location of concrete represented by the samples, 12.1.3 Date, time and name of individual molding specimens, 12.1.4 Slump, air content, and concrete temperature, test results and results of any other tests on the fresh concrete and any deviations from referenced standard test methods, and 12.1.5 Curing method. For standard curing method, report the initial curing method with maximum and minimum temperatures and final curing method. For field curing method, report the location where stored, manner of protection from the elements, temperature and moisture environment, and time of removal from molds. 13. Keywords 13.1 beams; casting samples; concrete; curing; cylinders; testing
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C31/C31M – 10 SUMMARY OF CHANGES Committee C09 has identified the location of selected changes to this practice since the last issue, C31/C31M–09, that may impact the use of this practice. (Approved October 1, 2010) (1) Revised 5.4 to further clarify the standard tamping rod description. Committee C09 has identified the location of selected changes to this practice since the last issue, C31/C31M – 08b, that may impact the use of this practice. (Approved May 1, 2009) (1) Revised 5.4, Table 1, and 9.4.1 so that similar wording is used in several standards regarding the requirements for the tamping rod.
(3) Revised 5.5 to change the vibrator frequency from 7000 vibrations per minute to 9000 vibrations per minute
(2) Added new Note 1 to describe an acceptable tamping rod length for several standards. ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone), 610-832-9555 (fax), or
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